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A126206
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Number of 4's in the decimal expansion of 4^n.
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7
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0, 1, 0, 1, 0, 1, 1, 1, 0, 2, 1, 3, 0, 1, 2, 2, 2, 1, 1, 3, 0, 3, 3, 3, 2, 2, 2, 3, 1, 2, 2, 3, 4, 3, 1, 3, 3, 4, 2, 4, 2, 4, 2, 2, 3, 4, 3, 3, 3, 3, 2, 2, 3, 5, 2, 4, 2, 4, 4, 3, 3, 3, 4, 4, 6, 5, 5, 4, 2, 9, 5, 2, 4, 6, 4, 7, 4, 2, 5, 4, 3, 4, 8, 4, 7, 9, 2, 8, 4, 7, 3, 10, 9, 5, 3, 5, 8, 8, 3, 10, 4
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OFFSET
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0,10
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LINKS
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EXAMPLE
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a(11)=3 because 4^11 = 4194304 with three 4's.
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MAPLE
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P:=proc(n) local i, k, x, y, w, cont; y:=4; k:=y; for i from 0 by 1 to n do x:=y^i; cont:=0; while x>0 do w:=x-trunc(x/10)*10; if w=k then cont:=cont+1; fi; x:=trunc(x/10); od; print(cont); od; end: P(100);
# Alternative:
map(n -> numboccur(4, convert(4^n, base, 10)), [$0..100]); # Robert Israel, Jul 18 2018
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MATHEMATICA
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DigitCount[4^#, 10, 4]&/@Range[0, 150] (* Harvey P. Dale, Feb 01 2011 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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